From left, Sen. Marco Rubio (R-Fla.), businessman Donald Trump and...

From left, Sen. Marco Rubio (R-Fla.), businessman Donald Trump and Sen. Ted Cruz (R-Texas) prepare for a Republican presidential primary debate at The University of Houston, Thursday, Feb. 25, 2016, in Houston. Credit: AP / David J. Phillip

Remember way back in the early days of this presidential slog when the Republican Party elite was boasting about its deep roster of talented candidates and how this would be a campaign of conservative ideas?

Now the elite is deliriously happy that there’s all this rasslin’ going on in Donald Trump’s muddy mosh pit.

My, how times have changed.

It’s all Trump’s fault, of course. He’s the one who changed the rules. Of campaigning. Of debating. Of branding. For months, he was given free rein to insult and demean before someone finally tried to play his game. Alas, it was poor Jeb Bush with his whiny patrician ineptness.

Ted Cruz then stuck a toe in those murky waters. And Trump kept cruising. Finally, Marco Rubio took his team’s opposition research on Trump and unloaded it on the billionaire at Thursday night’s GOP debate in Houston. And he kept on firing.

For once, it was Trump who was squirming. And for once, we had a GOP debate that was not about Hillary Clinton or prosecuting Hillary Clinton or anybody-but-Hillary Clinton. Instead of drawing contrasts with the Democratic front-runner and indicting her conflicts of interest and duplicity and complicated history and shifting views, the Republicans were doing that to each other.

Now let’s pause to consider the electorate for whom this is playing out. Yes, it’s divided. But one of those divisions is between those who mourn the current level of discourse and its abandonment of civility, and those who revel in the exuberant exchange of insults. And now it’s on, as the latter group says. This is politics as sport, or reality TV, and the idea is to score points and entertain, not inform. It’s the campaign as traveling circus.

Rubio has decided the only way to sideline Trump is to be the ringmaster with the bigger bullhorn. The only thing missing from his Houston assault was a catchy and concise moniker for Trump, something akin to “loser” or “liar.” That came the morning after, when Rubio showed he had no seller’s remorse for labeling Trump a con artist. And repeating it incessantly.

Whether anything sticks to Teflon Don is an open question. Trying to beat a master at his own game is always tricky. Sure enough, Trump’s genius at shifting the narrative when he hits rocky seas played out again when he announced Chris Christie’s endorsement. And that became the story for a while.

But the charges and countercharges levied in Houston will not wither soon. And they made clear once again that there are no skeleton-free campaigns. Bernie Sanders vs. John Kasich probably would be as close as you could get to that.

So Rubio hit Trump on his hiring of foreign workers to help build Trump Tower and to staff his Mar-a-Lago resort in Florida, the lawsuits he faces involving now-defunct Trump University, and his donations to the Clinton Foundation.

Trump slammed Rubio for credit-card debt and selling a house to a lobbyist for a big profit. He did not mention a letter Rubio wrote as a Florida legislator on official stationery asking state regulators to give a real estate license to a convicted cocaine dealer without divulging that the man was Rubio’s brother-in-law.

But that surely is coming. And who knows what else? We’re playing mud ball now. And remember: Rubio’s opposition research pales in comparison to Clinton’s. If you think Republicans were tough on Trump, the Clintons can be brutal.

In that respect, what happened in Houston might have been merely the warm-up act for what we’ll see this fall.

Michael Dobie is a member of Newsday’s editorial board.